Graphics glitching up in MW2 and L4D2.
 

I recently bought Left 4 Dead 2 and played that for an hour, but then when I played Modern Warfare 2, the graphics were all glitched up. Basically, there were these random lines popping up everywhere. All over the weapon models, player models, and all over the maps. The weird thing is that this didn't happen until today right when after installing L4D2.

http://thumbnails13.imagebam.com/612...8e61194870.gif

What's going on and how do I fix this problem?

BTW, my graphics card is a little old. It's a GeForce 8400M GS and I'm running on Windows Vista. However, it ran MW2 just fine on low settings. It ran COD4 and Left 4 Dead and Team Fortress 2 just fine as well on fairly low settings.

Does it do the weird line error after a restart? Occasionally I have problems running one game after another, though a restart almost always fixes it.

If it's a little old you may want to check how much dust your card has accumulated. Erratic lines and broken polygons can be a tell tale sign of your graphics card overheating, or on its way out.

I actually did that a few weeks ago and it was fixed. However, the graphics started to glitch up again two days ago. I updated my drivers, but I'm still having problems.

I've had my laptop for nearly two years, would it already be time for me to get a new one? Seems a little too early to do so, right? ...Then again, I'm not an expert on this kind of stuff, so what do I now... :/